I wouldn't spend much on it. You need a new wheelset, new RD, new crank, and still want to upgrade from stem to DT shifters. Unless you have the parts laying about and can do the work yourself, it'll add up to way more than the bike is worth. And it'll still be ugly......

Keep it running, and look for a better bike at all the usual places - thrifts, garage sales, etc.

In the meantime, I can check my parts bin and see if I have a RD and mtb crankset (you can remove the small ring) that I can send your way.